Barrier film for electronic devices and substrates

ABSTRACT

Methods for forming a coating over a surface are disclosed. A method includes directing a first source of barrier film material toward a substrate in a first direction at an angle θ relative to the substrate, wherein θ is greater than about 0° and less than about 85°. Additionally, a method of depositing a barrier film over a substrate includes directing a plurality of N sources of barrier film material toward a substrate, each source being directed at an angle θ N  relative to the substrate, wherein for each θ N , θ is greater than about 0° and less than about 180°. For at least a first of the θ N , θ N  is greater than about 0° and less than about 85°, and for at least a second of the θ N , θ N  is greater than about 95° and less than about 180°.

PRIORITY

This application claims priority to U.S. Provisional Application No.61/705,463, filed Sep. 25, 2012, the disclosure of which is incorporatedby reference in its entirety.

The claimed invention was made by, on behalf of, and/or in connectionwith one or more of the following parties to a joint universitycorporation research agreement: Regents of the University of Michigan,Princeton University, The University of Southern California, and theUniversal Display Corporation. The agreement was in effect on and beforethe date the claimed invention was made, and the claimed invention wasmade as a result of activities undertaken within the scope of theagreement.

FIELD OF THE INVENTION

The present invention relates to barrier coatings for substrates andelectronic devices.

BACKGROUND

Opto-electronic devices that make use of organic materials are becomingincreasingly desirable for a number of reasons. Many of the materialsused to make such devices are relatively inexpensive, so organicopto-electronic devices have the potential for cost advantages overinorganic devices. In addition, the inherent properties of organicmaterials, such as their flexibility, may make them well suited forparticular applications such as fabrication on a flexible substrate.Examples of organic opto-electronic devices include organic lightemitting devices (OLEDs), organic phototransistors, organic photovoltaiccells, and organic photodetectors. For OLEDs, the organic materials mayhave performance advantages over conventional materials. For example,the wavelength at which an organic emissive layer emits light maygenerally be readily tuned with appropriate dopants.

OLEDs make use of thin organic films that emit light when voltage isapplied across the device. OLEDs are becoming an increasinglyinteresting technology for use in applications such as flat paneldisplays, illumination, and backlighting. Several OLED materials andconfigurations are described in U.S. Pat. Nos. 5,844,363, 6,303,238, and5,707,745, which are incorporated herein by reference in their entirety.

One application for phosphorescent emissive molecules is a full colordisplay. Industry standards for such a display call for pixels adaptedto emit particular colors, referred to as “saturated” colors. Inparticular, these standards call for saturated red, green, and bluepixels. Color may be measured using CIE coordinates, which are wellknown to the art.

One example of a green emissive molecule istris(2-phenylpyridine)iridium, denoted Ir(ppy)₃, which has the followingstructure:

In this, and later figures herein, we depict the dative bond fromnitrogen to metal (here, Ir) as a straight line.

More details on OLEDs, and the definitions described above, can be foundin U.S. Pat. No. 7,279,704, which is incorporated herein by reference inits entirety.

SUMMARY OF THE INVENTION

In one aspect, a method of depositing a barrier film over a substrate isprovided. The method includes directing a first source of barrier filmmaterial toward a substrate in a first direction at an angle θ relativeto the substrate, wherein 0°<θ<85°. In an aspect, 30°<θ<60°.

In an aspect, directing the first source may be performed using a plasmadeposition process, an atomic layer deposition process, and the like. Inan aspect, directing the barrier film material toward the substratecauses a single-layer barrier film to be deposited over the substrate.

In an aspect, the barrier film material may comprise a material typesuch as an oxide, a nitride, a ceramic, and an organic-inorganic hybrid.In an aspect, the barrier film material has a water vapor transmissionrate of not more than 10⁻² g/day/m².

In an aspect, the method of depositing a barrier film over a substratefurther includes directing a second source of barrier film materialtoward a substrate in a second direction at an angle φ relative to thesubstrate, wherein 95°<φ<180°. In an aspect, 120°<φ<150°. In anotheraspect, 85°<φ<95°.

In an aspect, the second source of barrier film material is the same asthe first source of barrier film material.

In an aspect, subsequent to directing the first source of barrier filmmaterial toward the substrate, rotating the substrate through an angleequal to φ−θ.

In an aspect, subsequent to directing the first source of barrier filmmaterial toward the substrate, rotating the first source of barrier filmmaterial through an angle equal to φ−θ.

In an aspect, subsequent to directing the first source of barrier filmmaterial toward the substrate, rotating the substrate in the plane ofthe substrate.

In an aspect, providing an electric field having a field direction, andproviding the substrate at the angle θ relative to the field direction.

In another aspect, the substrate comprises a substantially planar firstportion and a substantially non-planar second portion. In an aspect, thesubstantially non-planar second portion comprises a particle disposedover the first portion.

In an aspect, the substrate comprises an OLED and the OLED may beflexible. In an aspect, the substrate is flexible. In an aspect, themethod of depositing a barrier film over a substrate further includes astep of depositing an OLED over the substrate.

In an aspect, a method of depositing a barrier film over a substrateincludes directing a plurality of N sources of barrier film materialtoward a substrate, each source being directed at an angle θ_(N)relative to the substrate, wherein for each θ_(N), 0°<θ<180°, and for atleast a first of the θ_(N), 0°<θ_(N)<85°. In an aspect, for at least asecond of the θ_(N), 95°<θ_(N)<180°.

In an aspect, a deposition system includes a first source of barrierfilm material configured to direct a barrier film material in a firstdirection, and a substrate support, wherein the first source of barrierfilm material and the substrate support are positionable to form arelative angle θ between the first direction and a substrate supportedby the substrate support, and wherein 0°<θ<85°. In an aspect, 30°<θ<60°.

In an aspect, the first source comprises an electric field generatorconfigured to generate an electric field having a field direction in thefirst direction.

In an aspect, the first source is fixed, and the substrate support ispositionable relative to the first source.

In an aspect, configuring the first source of barrier film material todirect a barrier film material in the first direction is performed usinga plasma deposition process. In an aspect, the first source of barrierfilm material is configured to direct a barrier film material in thefirst direction is performed using an atomic layer deposition process.

In an aspect, the barrier film material comprises a material typeselected from the group consisting of: an oxide, a nitride, a ceramic,and an organic-inorganic hybrid. In an aspect, the barrier film materialhas a water vapor transmission rate of not more than 10-2 g/day/m2. Inanother aspect, directing the barrier film material toward the substratecauses a single-layer barrier film to be deposited over the substrate.

In another aspect, a deposition system further includes a second sourceof barrier film material configured to direct a barrier film material ina second direction, wherein the second source of barrier film materialand the substrate support are positionable to form a relative angle φbetween the second direction and the substrate supported by thesubstrate support, and wherein 95°<φ<180°. In an aspect, 120°<φ<150°.

In an aspect, the second source of barrier film material is the same asthe first source of barrier film material.

In an aspect, a second source of barrier film material may be configuredto direct a barrier film material in a second direction, wherein thesecond source of barrier film material and the substrate support arepositionable to form a relative angle φ between the second direction andthe substrate supported by the substrate support, and, wherein85°<φ<95°.

In another aspect, a deposition system further includes subsequent todirecting the first source of barrier film material toward thesubstrate, rotating the substrate through an angle equal to φ−θ. In anaspect, subsequent to directing the first source of barrier filmmaterial toward the substrate, rotating the first source of barrier filmmaterial through an angle equal to φ−θ.

In an aspect, subsequent to directing the first source of barrier filmmaterial toward the substrate, rotating the substrate in the plane ofthe substrate. In an aspect, the substrate comprises a substantiallyplanar first portion and a substantially non-planar second portion. Inan aspect, the substantially non-planar second portion comprises aparticle disposed over the first portion.

In an aspect, the substrate comprises an OLED. In an aspect, the OLEDmay be flexible and/or the substrate may be flexible. In an aspect, thesystem may further include a step of depositing an OLED over thesubstrate.

In an aspect, a system for depositing a barrier film over a substrateincludes a plurality of N sources of barrier film material, each sourceconfigured to direct a barrier film material in a direction, and asubstrate support, wherein each source of barrier film material and thesubstrate support are positionable to form a relative angle θ_(N)between the direction and a substrate supported by the substratesupport, and wherein for each θ_(N), 0°<θ<180°, and for at least a firstof the θ_(N), 0°<θ_(N)<85°. In an aspect, for at least a second of theθ_(N), 95°<θ_(N)<180°.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an organic light emitting device.

FIG. 2 shows an inverted organic light emitting device that does nothave a separate electron transport layer.

FIGS. 3( a) and (b) show a schematic depiction of a substrate having aparticle and in relative motion with respect to two angular sources.

FIGS. 4( a) and (b) show a Si wafer loaded on a substrate support.

FIG. 5 shows a schematic cross-section of a film coating of a substratewith deposition on the top, side, and bottom surfaces.

FIGS. 6( a) and (b) show SEM cross-sectional micrographs of barrier filmon a Si wafer.

FIGS. 7( a) and (b) show SEM cross-sectional micrographs of barrier filmon a Si wafer.

FIGS. 8( a), (b), and (c) show a schematic depiction of a substratehaving a particle and incoming ions from varying directions.

DETAILED DESCRIPTION

Generally, an OLED comprises at least one organic layer disposed betweenand electrically connected to an anode and a cathode. When a current isapplied, the anode injects holes and the cathode injects electrons intothe organic layer(s). The injected holes and electrons each migratetoward the oppositely charged electrode. When an electron and holelocalize on the same molecule, an “exciton,” which is a localizedelectron-hole pair having an excited energy state, is formed. Light isemitted when the exciton relaxes via a photoemissive mechanism. In somecases, the exciton may be localized on an excimer or an exciplex.Non-radiative mechanisms, such as thermal relaxation, may also occur,but are generally considered undesirable.

The initial OLEDs used emissive molecules that emitted light from theirsinglet states (“fluorescence”) as disclosed, for example, in U.S. Pat.No. 4,769,292, which is incorporated by reference in its entirety.Fluorescent emission generally occurs in a time frame of less than 10nanoseconds.

More recently, OLEDs having emissive materials that emit light fromtriplet states (“phosphorescence”) have been demonstrated. Baldo et al.,“Highly Efficient Phosphorescent Emission from OrganicElectroluminescent Devices,” Nature, vol. 395, 151-154, 1998;(“Baldo-I”) and Baldo et al., “Very high-efficiency green organiclight-emitting devices based on electrophosphorescence,” Appl. Phys.Lett., vol. 75, No. 3, 4-6 (1999) (“Baldo-II”), which are incorporatedby reference in their entireties. Phosphorescence is described in moredetail in U.S. Pat. No. 7,279,704 at cols. 5-6, which are incorporatedby reference.

As used herein, the term “organic” includes polymeric materials as wellas small molecule organic materials that may be used to fabricateorganic opto-electronic devices. “Small molecule” refers to any organicmaterial that is not a polymer, and “small molecules” may actually bequite large. Small molecules may include repeat units in somecircumstances. For example, using a long chain alkyl group as asubstituent does not remove a molecule from the “small molecule” class.Small molecules may also be incorporated into polymers, for example as apendent group on a polymer backbone or as a part of the backbone. Smallmolecules may also serve as the core moiety of a dendrimer, whichconsists of a series of chemical shells built on the core moiety. Thecore moiety of a dendrimer may be a fluorescent or phosphorescent smallmolecule emitter. A dendrimer may be a “small molecule,” and it isbelieved that all dendrimers currently used in the field of OLEDs aresmall molecules.

As used herein, “top” means furthest away from the substrate, while“bottom” means closest to the substrate. Where a first layer isdescribed as “disposed over” a second layer, the first layer is disposedfurther away from substrate. There may be other layers between the firstand second layer, unless it is specified that the first layer is “incontact with” the second layer. For example, a cathode may be describedas “disposed over” an anode, even though there are various organiclayers in between.

As used herein, “solution processible” means capable of being dissolved,dispersed, or transported in and/or deposited from a liquid medium,either in solution or suspension form.

A ligand may be referred to as “photoactive” when it is believed thatthe ligand directly contributes to the photoactive properties of anemissive material. A ligand may be referred to as “ancillary” when it isbelieved that the ligand does not contribute to the photoactiveproperties of an emissive material, although an ancillary ligand mayalter the properties of a photoactive ligand.

As used herein, and as would be generally understood by one skilled inthe art, a first “Highest Occupied Molecular Orbital” (HOMO) or “LowestUnoccupied Molecular Orbital” (LUMO) energy level is “greater than” or“higher than” a second HOMO or LUMO energy level if the first energylevel is closer to the vacuum energy level. Since ionization potentials(IP) are measured as a negative energy relative to a vacuum level, ahigher HOMO energy level corresponds to an IP having a smaller absolutevalue (an IP that is less negative). Similarly, a higher LUMO energylevel corresponds to an electron affinity (EA) having a smaller absolutevalue (an EA that is less negative). On a conventional energy leveldiagram, with the vacuum level at the top, the LUMO energy level of amaterial is higher than the HOMO energy level of the same material. A“higher” HOMO or LUMO energy level appears closer to the top of such adiagram than a “lower” HOMO or LUMO energy level.

As used herein, and as would be generally understood by one skilled inthe art, a first work function is “greater than” or “higher than” asecond work function if the first work function has a higher absolutevalue. Because work functions are generally measured as negative numbersrelative to vacuum level, this means that a “higher” work function ismore negative. On a conventional energy level diagram, with the vacuumlevel at the top, a “higher” work function is illustrated as furtheraway from the vacuum level in the downward direction. Thus, thedefinitions of HOMO and LUMO energy levels follow a different conventionthan work functions.

FIG. 1 shows an organic light emitting device 100. The figures are notnecessarily drawn to scale. Device 100 may include a substrate 110, ananode 115, a hole injection layer 120, a hole transport layer 125, anelectron blocking layer 130, an emissive layer 135, a hole blockinglayer 140, an electron transport layer 145, an electron injection layer150, a protective layer 155, a cathode 160, and a barrier layer 170.Cathode 160 is a compound cathode having a first conductive layer 162and a second conductive layer 164. Device 100 may be fabricated bydepositing the layers described, in order. The properties and functionsof these various layers, as well as example materials, are described inmore detail in U.S. Pat. No. 7,279,704 at cols. 6-10, which areincorporated by reference.

More examples for each of these layers are available. For example, aflexible and transparent substrate-anode combination is disclosed inU.S. Pat. No. 5,844,363, which is incorporated by reference in itsentirety. An example of a p-doped hole transport layer is m-MTDATA dopedwith F₄-TCNQ at a molar ratio of 50:1, as disclosed in U.S. PatentApplication Publication No. 2003/0230980, which is incorporated byreference in its entirety. Examples of emissive and host materials aredisclosed in U.S. Pat. No. 6,303,238 to Thompson et al., which isincorporated by reference in its entirety. An example of an n-dopedelectron transport layer is BPhen doped with Li at a molar ratio of 1:1,as disclosed in U.S. Patent Application Publication No. 2003/0230980,which is incorporated by reference in its entirety. U.S. Pat. Nos.5,703,436 and 5,707,745, which are incorporated by reference in theirentireties, disclose examples of cathodes including compound cathodeshaving a thin layer of metal such as Mg:Ag with an overlyingtransparent, electrically-conductive, sputter-deposited ITO layer. Thetheory and use of blocking layers is described in more detail in U.S.Pat. No. 6,097,147 and U.S. Patent Application Publication No.2003/0230980, which are incorporated by reference in their entireties.Examples of injection layers are provided in U.S. Patent ApplicationPublication No. 2004/0174116, which is incorporated by reference in itsentirety. A description of protective layers may be found in U.S. PatentApplication Publication No. 2004/0174116, which is incorporated byreference in its entirety.

FIG. 2 shows an inverted OLED 200. The device includes a substrate 210,a cathode 215, an emissive layer 220, a hole transport layer 225, and ananode 230. Device 200 may be fabricated by depositing the layersdescribed, in order. Because the most common OLED configuration has acathode disposed over the anode, and device 200 has cathode 215 disposedunder anode 230, device 200 may be referred to as an “inverted” OLED.Materials similar to those described with respect to device 100 may beused in the corresponding layers of device 200. FIG. 2 provides oneexample of how some layers may be omitted from the structure of device100.

The simple layered structure illustrated in FIGS. 1 and 2 is provided byway of non-limiting example, and it is understood that embodiments ofthe invention may be used in connection with a wide variety of otherstructures. The specific materials and structures described areexemplary in nature, and other materials and structures may be used.Functional OLEDs may be achieved by combining the various layersdescribed in different ways, or layers may be omitted entirely, based ondesign, performance, and cost factors. Other layers not specificallydescribed may also be included. Materials other than those specificallydescribed may be used. Although many of the examples provided hereindescribe various layers as comprising a single material, it isunderstood that combinations of materials, such as a mixture of host anddopant, or more generally a mixture, may be used. Also, the layers mayhave various sublayers. The names given to the various layers herein arenot intended to be strictly limiting. For example, in device 200, holetransport layer 225 transports holes and injects holes into emissivelayer 220, and may be described as a hole transport layer or a holeinjection layer. In one embodiment, an OLED may be described as havingan “organic layer” disposed between a cathode and an anode. This organiclayer may comprise a single layer, or may further comprise multiplelayers of different organic materials as described, for example, withrespect to FIGS. 1 and 2.

Structures and materials not specifically described may also be used,such as OLEDs comprised of polymeric materials (PLEDs) such as disclosedin U.S. Pat. No. 5,247,190 to Friend et al., which is incorporated byreference in its entirety. By way of further example, OLEDs having asingle organic layer may be used. OLEDs may be stacked, for example asdescribed in U.S. Pat. No. 5,707,745 to Forrest et al, which isincorporated by reference in its entirety. The OLED structure maydeviate from the simple layered structure illustrated in FIGS. 1 and 2.For example, the substrate may include an angled reflective surface toimprove out-coupling, such as a mesa structure as described in U.S. Pat.No. 6,091,195 to Forrest et al., and/or a pit structure as described inU.S. Pat. No. 5,834,893 to Bulovic et al., which are incorporated byreference in their entireties.

Unless otherwise specified, any of the layers of the various embodimentsmay be deposited by any suitable method. For the organic layers,preferred methods include thermal evaporation, ink-jet, such asdescribed in U.S. Pat. Nos. 6,013,982 and 6,087,196, which areincorporated by reference in their entireties, organic vapor phasedeposition (OVPD), such as described in U.S. Pat. No. 6,337,102 toForrest et al., which is incorporated by reference in its entirety, anddeposition by organic vapor jet printing (OVJP), such as described inU.S. Pat. No. 7,431,968, which is incorporated by reference in itsentirety. Other suitable deposition methods include spin coating andother solution based processes. Solution based processes are preferablycarried out in nitrogen or an inert atmosphere. For the other layers,preferred methods include thermal evaporation. Preferred patterningmethods include deposition through a mask, cold welding such asdescribed in U.S. Pat. Nos. 6,294,398 and 6,468,819, which areincorporated by reference in their entireties, and patterning associatedwith some of the deposition methods such as ink-jet and OVJP. Othermethods may also be used. The materials to be deposited may be modifiedto make them compatible with a particular deposition method. Forexample, substituents such as alkyl and aryl groups, branched orunbranched, and preferably containing at least 3 carbons, may be used insmall molecules to enhance their ability to undergo solution processing.Substituents having 20 carbons or more may be used, and 3-20 carbons isa preferred range. Materials with asymmetric structures may have bettersolution processibility than those having symmetric structures, becauseasymmetric materials may have a lower tendency to recrystallize.Dendrimer substituents may be used to enhance the ability of smallmolecules to undergo solution processing.

Devices fabricated in accordance with embodiments of the presentinvention may further optionally comprise a barrier layer. One purposeof the barrier layer is to protect the electrodes and organic layersfrom damaging exposure to harmful species in the environment includingmoisture, vapor and/or gases, etc. The barrier layer may be depositedover, under or next to a substrate, an electrode, or over any otherparts of a device including an edge. The barrier layer may comprise asingle layer, or multiple layers. The barrier layer may be formed byvarious known chemical vapor deposition techniques and may includecompositions having a single phase as well as compositions havingmultiple phases. Any suitable material or combination of materials maybe used for the barrier layer. The barrier layer may incorporate aninorganic or an organic compound or both. The preferred barrier layercomprises a mixture of a polymeric material and a non-polymeric materialas described in U.S. Pat. No. 7,968,146, PCT Pat. Application Nos.PCT/US2007/023098 and PCT/US2009/042829, which are herein incorporatedby reference in their entireties. To be considered a “mixture”, theaforesaid polymeric and non-polymeric materials comprising the barrierlayer should be deposited under the same reaction conditions and/or atthe same time. The weight ratio of polymeric to non-polymeric materialmay be in the range of 95:5 to 5:95. The polymeric material and thenon-polymeric material may be created from the same precursor material.In one example, the mixture of a polymeric material and a non-polymericmaterial consists essentially of polymeric silicon and inorganicsilicon.

Devices fabricated in accordance with embodiments of the invention maybe incorporated into a wide variety of consumer products, including flatpanel displays, computer monitors, medical monitors, televisions,billboards, lights for interior or exterior illumination and/orsignaling, heads up displays, fully transparent displays, flexibledisplays, laser printers, telephones, cell phones, personal digitalassistants (PDAs), laptop computers, digital cameras, camcorders,viewfinders, micro-displays, 3-D displays, vehicles, a large area wall,theater or stadium screen, or a sign. Various control mechanisms may beused to control devices fabricated in accordance with the presentinvention, including passive matrix and active matrix. Many of thedevices are intended for use in a temperature range comfortable tohumans, such as 18 degrees C. to 30 degrees C., and more preferably atroom temperature (20-25 degrees C.), but could be used outside thistemperature range, for example, from −40 degrees C. to +80 degrees C.

The materials and structures described herein may have applications indevices other than OLEDs. For example, other optoelectronic devices suchas organic solar cells and organic photodetectors may employ thematerials and structures. More generally, organic devices, such asorganic transistors, may employ the materials and structures.

The terms halo, halogen, alkyl, cycloalkyl, alkenyl, alkynyl, aralkyl,heterocyclic group, aryl, aromatic group, and heteroaryl are known tothe art, and are defined in U.S. Pat. No. 7,279,704 at cols. 31-32,which are incorporated herein by reference.

In general, OLEDs and other water sensitive devices can degrade uponstorage. Encapsulating OLEDs and other water sensitive devices can helpto prolong their shelf life. Glass encapsulation is useful for brittledevices made on glass but is not ideal for flexible or shatter-proofdevices. Thin barrier films can be used for such flexible and/orshatter-proof devices. Many new thin film encapsulation barriers havebeen reported over the past decade with water vapor transmission rates(WVTR) suitable for electronic devices such as OLEDs and solar cells.However, particulate contamination is a major challenge in thin filmencapsulation of electronic devices and substrates. Particles thickerthan the thin film barrier can remain partially encapsulated and allowfor easy passage of water vapor and other atmospheric gases, therebyleading to the formation of defects such as dark spots in OLEDs.Alternatively, growing very thick inorganic layers in order tocompletely encapsulate a particle that is several microns thick may notbe possible because brittle inorganic films may not remain micro-crackfree beyond a certain thickness. One option may be to use polymerlayers, which can be evaporated at very high deposition rates and/orspun on to fully encapsulate particles. Such a technique is utilized inmultilayer barriers where alternate layers of inorganic and polymerfilms are used. Although multilayer barrier films are suitable forparticle coverage, they suffer from other problems such as edge ingress(permeation along the edge), cost effectiveness, and commercialfeasibility.

Additionally, moisture and oxygen each have a very low diffusion lengththrough a hybrid layer and hence a hybrid layer having sub-micronthickness may be sufficient to encapsulate a flat surface withoutparticles; however, this is not typical. Under typical conditions, asubstrate will accumulate particles, and these particles candetrimentally affect the growth profile of the film. For example,consider a particle sitting on a substrate. When the substrate ismounted perpendicular to the direction of plasma deposition, thisconfiguration broadly results in at least two types of surfaces; exposedsurfaces and unexposed surfaces. Exposed surfaces are surfaces in directcontact with plasma and unexposed surfaces refer to surfaces not indirect contact with plasma. In a plasma deposition process, the exposedsurfaces are deposited with a film having a thickness greater than afilm deposited on the unexposed surfaces. This varying film thicknesscan lead to improper or partial coverage of particles.

The present disclosure provides methods for depositing a barrier layerand other single layer barrier films. In particular, the embodimentsdisclosed herein achieve more uniform coverage of substrates andparticles, and may be useful in OLEDs, solar cells, or any substratewhich may need a permeation barrier. This results in reduced passage ofwater vapor and other atmospheric gases, thereby preventing defects suchas dark spots in OLEDs. In particular, the disclosed methods allow forcomplete encapsulation of particles without the need for a thick film.According to the disclosed methods, single layer barrier films can bemade to encapsulate particles, thereby eliminating the need for polymerfilms (such as a multilayer barrier) to cover particles.

An example of a barrier layer is a single layer barrier deposited in asingle chamber CVD system. This single chamber CVD system utilizes thesame precursor, for example a siloxane, throughout the film depositionprocess. This particular single layer barrier has hybrid qualitiesbecause it has two phases, one that is partly oxide-like and anotherthat is partly polymer-like. Both phases are intimately mixed at amolecular level, thus resulting in a hybrid single layer barrier ratherthan a multilayer film. An example of such a barrier film is describedin US20080102223 A1, which is incorporated by reference in its entirety.Other examples of barrier films are described in U.S. Pat. No. 7,968,146and U.S. Pat. No. 6,548,912, which are incorporated by reference intheir entirety.

For example, it is possible to form a hybrid layer of hybridpolymeric/nonpolymeric character and having characteristics suitable foruse in various applications. Such characteristics include opticaltransparency (e.g., in some cases, the hybrid layer is opticallytransparent), impermeability, flexibility, thickness, adhesion, andother mechanical properties. For example, one or more of thesecharacteristics may be adjusted by varying the weight % of polymericmaterial in the hybrid layer, with the remainder being non-polymericmaterial. For instance, to achieve a desired level of flexibility andimpermeability, the wt % polymeric material may preferably be in therange of 5 to 95%, and more preferably in the range of 10 to 25%.However, other ranges are also possible depending upon the application.

As another example, barrier layers made of purely non-polymericmaterials, such as silicon oxide, can have various advantages relatingto optical transparency, good adhesion, and good film stress. However,these non-polymeric layers tend to contain microscopic defects whichallow the diffusion of water vapor and oxygen through the layer.Providing some polymeric character to the non-polymeric layer can reducethe permeability of the layer without significantly altering theadvantageous properties of a purely non-polymeric layer. In general, alayer having hybrid polymeric/non-polymeric characteristics reduces thepermeability of the layer by reducing the size and/or number of defects,in particular microcracks. Furthermore, a barrier film material may beany other barrier film material not discussed herein.

According to an embodiment of the present disclosure, a method ofdepositing a barrier film over a substrate is provided. As discussedthroughout, embodiments disclosed herein provide for deposition ofbarrier material on a substrate at various angles of deposition relativeto a substrate, and these various angles of deposition are broadlyapplicable to all embodiments discussed herein. FIGS. 3( a) and 3(b)show a schematic depiction of a substrate in relative motion withrespect to two angular sources according to an embodiment of the presentdisclosure.

As shown in FIG. 3( a), an embodiment includes directing a first source320 and second source 330 of barrier film material 340 toward asubstrate 300 having a particle 310 upon its surface. The substrate isin motion relative to the first and second sources 320, 330. As shown,in this example the substrate is moving to the right while the sources320, 330 are stationary. More generally, any of the sources and/orsubstrate may be moved relative to the other. In general, the substrate300 may include a substantially planar first portion and a substantiallynon-planar second portion. As an example, the substantially non-planarsecond portion may include a particle 310 disposed over the firstportion. As shown in FIG. 3( b), the first source 320 of barrier filmmaterial 340 may be directed in a first direction at an angle θ relativeto the substrate 300. In some embodiments, θ may be greater than about0° and less than about 85°, θ may be greater than about 15° and lessthan about 85°, θ may be greater than about 30° and less than about 85°.In some embodiments, θ may be greater than about 15° and less than about30°, θ may be greater than about 15° and less than about 60°, θ may begreater than about 30° and less than about 45°, θ may be greater thanabout 30° and less than about 60°. In some embodiments, θ may be 45°, θmay be 30°, or θ may be 15°. In some embodiments, θ may be about 45°, θmay be about 30°, or θ may be about 15°. Directing the barrier filmmaterial 340 toward the substrate 300 may cause a barrier film 340 to bedeposited over the substrate 300 and the particle 310. As shown, thefirst source 320 directs barrier film material generally toward and atan angle to the substrate, to coat a portion of the particle 310 and thesubstrate 300. In some instances, the first source may include anelectric field generator configured to generate an electric field havinga field direction in the first direction. Similarly, an electric fieldmay be generated by a source distinct from the sources. The barrier filmmaterial ejected by the sources may be charged prior to ejection, suchthat the electric field causes the material to follow the pathindicated, and/or to otherwise deposit on desired areas of thesubstrate.

In an embodiment, as shown in FIG. 3( a) an embodiment may also includedirecting a second source 330 of barrier film material 350 toward thesubstrate 300. As shown in FIG. 3( b), the second source 330 of barrierfilm material 350 may be directed in a second direction at an angle φrelative to the substrate 300. In an embodiment, φ may be greater thanabout 95° and less than about 180°, greater than about 95° and less thanabout 120°, greater than about 120° and less than about 150°, andgreater than about 85° and less than about 95°. In some embodiments, φmay be 85°, φ may be 90°, φ may be 95°, φ may be 120°, φ may be 135°, φmay be 150°, and φ may be 165°. As shown, the second source 330 directsbarrier film material 350 to coat another portion of the particle 310and the substrate 300. The use of multiple sources thus may provide moreextensive and/or uniform coverage of the non-planar portion of thesubstrate, while still maintaining uniform coverage of the planarportion. In some instances, the second source of barrier film materialmay be the same as the first source of barrier film material.

According to an embodiment of the present disclosure, a depositionsystem may include a first source of barrier film material configured todirect a barrier film material in a first direction and a substratesupport. The first source of barrier film material and the substratesupport may be positionable to form a relative angle θ between the firstdirection and a substrate supported by the substrate support aspreviously described. The relative angle θ may be greater than about 0°and less than about 85°.

In an embodiment, the deposition system described above may include asecond source of barrier film material configured to direct a barrierfilm material in a second direction as previously described with respectto FIG. 3. The second source of barrier film material and the substratesupport may be positionable to form a relative angle φ between thesecond direction and the substrate supported by the substrate support.The relative angle φ may be greater than about 95° and less than about180°. In an implementation, φ may be greater than about 120° and lessthan about 150°, and φ may be greater than about 85° and less than about95°.

According to an implementation the first source may be fixed, and thesubstrate support may be positionable relative to the first source. Inorder to achieve more uniform coverage of non-planar portions of asubstrate, such as particles disposed on the substrate, subsequent todirecting the first source of barrier film material toward thesubstrate, the substrate may be rotated through an angle equal to φ−θ.As shown in FIGS. 4( a) and 4(b), a substrate 410 may be loaded on asubstrate support 400. FIG. 4( b) shows that the substrate 410 may bepositionable to create an angle relative to a field of directionassociated with a source of barrier film material. Additionally, thesubstrate may be rotated in the plane of the substrate, for example toallow a single source of barrier film material to direct material towardmultiple sides or portions of a non-planar portion of the substrate. Forexample, considering a single particle disposed on a substrate, thesubstrate may be rotated in the plane of the substrate to allow a singlesource of barrier film material to direct material toward every regionof the outside of the particle. Further, subsequent to directing thefirst source of barrier film material toward the substrate, the firstsource of barrier film material may be rotated through an angle equal toφ−θ.

More generally, a plurality of sources of barrier film or films may bedirected toward a substrate at various angles. Such an arrangement mayprovide for more efficient and/or uniform coating of a non-planarsubstrate. According to an embodiment, a method of depositing a barrierfilm over a substrate may include directing a plurality of N sources ofbarrier film material toward a substrate, each source being directed atan angle θ_(n) specific to the source, relative to the substrate. Thatis, each source may be disposed at an angle that is specific to thesource, which may or may not be the same as the angle at which any otherof the N sources is arranged. In particular, for each angle θ_(n), θ_(n)may be greater than 0° and less than 180°. For at least a first of theangles θ₁ at which a first source is arranged, θ₁ may be greater thanabout 0° and less than about 85°. For at least a second of the angles θ₂of a second source, θ₂ may be greater than about 95° and less than about180°.

In an embodiment, a system for depositing a barrier film over asubstrate is provided. The system may include a plurality of N sourcesof barrier film material, each of which is configured to direct abarrier film material in a direction. Each source of barrier filmmaterial may be positionable to form a relative angle θ_(n), specific tothe source, between the direction of the source and a substratesupported by a substrate support as previously described. For each ofthe angles, the relative angle θ_(n) may be greater than about 0° andless than about 180°. In particular, for at least a first of the anglesθ₁, θ₁ may be greater than about 0° and less than about 85°. Further,for at least a second of the angles θ₂, θ₂ may be greater than about 95°and less than about 180°. As an example, a deposition system may include4 sources of barrier film material; each source may be directed towardsa substrate. Each source may be configured to form an angle θ, specificto each source, relative to the substrate. The first source may bedirected towards the substrate at an angle θ₁ of 30°, the second sourcemay be directed towards the substrate at an angle θ₂ of 110°, the thirdsource may be directed towards the substrate at an angle θ₃ of 80°, thefourth source may be directed towards the substrate at an angle θ₄ of90°.

As discussed above, directing and/or configuring the first source ofbarrier film material toward a substrate may be performed using a plasmadeposition process, an atomic layer deposition process, and any otherprocess for directing and/or configuring a source of barrier filmmaterial toward a substrate.

In general, the barrier film material may be any of the barrier filmmaterials discussed herein. Specifically, the barrier film material mayinclude a material type including one or more of an oxide, a nitride, aceramic, and an organic-inorganic hybrid. Additionally, in anembodiment, the barrier film material has a water vapor transmissionrate of not more than about 10⁻² g/day/m². In some embodiments, thebarrier film material may have a water vapor transmission rate of notmore than about 10⁻⁴ g/day/m², 10⁻⁵ g/day/m² , or 10⁻⁶ g/day/m².

Furthermore, the substrate described above may be flexible. Thesubstrate may include an OLED, and the OLED may be flexible. In anembodiment, the method described above may also include a step ofdepositing an OLED over the substrate.

Experimental

For better coverage of a particle, in an aspect, it is desirable to havesufficient barrier film deposition in the plasma shadow regions, whichare the underside regions of particles. An increase in the filmthickness in the plasma shadow regions was achieved by modifying theorientation of the plasma shadow region with respect to the source ofincoming ions and other species associated with the plasma. Thefollowing experiments show the impact of changing the orientation of theplasma shadow region to make it more accessible to plasma species from asource.

Two Si wafers were placed in our deposition system. One Si wafer wasloaded as shown in FIG. 4( a). Although not shown in FIG. 4( a), thewafer was loaded perpendicular to the direction of electric fieldassociated with plasma from a source. As shown in FIG. 4( b), one Siwafer was loaded at an angle. Although not shown in FIG. 4( b), thiswafer was loaded at an acute angle with the electric field associatedwith plasma from a source. Barrier films were grown on both Si wafersand the thicknesses of each of the resulting films was measured on topand bottom of the wafer. Additionally, the ratio of film thicknesses inthe two regions was calculated. Although the barrier film described inUS20080102223 A1 was grown on both Si wafers for this experiment, anyother barrier film suitable for deposition may be used in the disclosedmethod. FIG. 5 shows the schematic cross-section of film 510 grown on aSi wafer 500 loaded perpendicular to the direction of electric fieldassociated with plasma from a source. FIG. 5 depicts the change in thethickness of the film 510 from the top side (facing the plasma) to thebottom side (not facing the plasma). As shown in FIG. 5, the portion ofthe film 510 on the surface facing the plasma source is thicker. Similarcross-sections of films grown on Si wafers are discussed below withregard to FIGS. 6 and 7 in both the perpendicular and angularorientations, respectively.

Furthermore, FIGS. 6(A) and 6(B) shows the SEM cross-sectionalmicrographs of barrier film on the Si wafer loaded as in FIG. 4( a),i.e., perpendicular to the direction of electric field associated withplasma from a source. FIG. 6(A) shows the thickness of the barrier filmof 1.503 μm on the top surface facing the plasma. FIG. 6(B) shows thethickness of the barrier film of 148.8 nm on the bottom surface facingaway from the plasma. The ratio of the thicknesses of the film on thetop and bottom surfaces is greater than 10.

FIGS. 7(A) and 7(B) show the SEM cross-sectional micrographs of barrierfilm on Si wafer loaded as in FIG. 4( b), i.e., making an acute anglewith the electric field associated with plasma from a source. FIG. 7(A)shows the thickness of the barrier film of 2.266 μm on the top surfacefacing the plasma. FIG. 7(B) shows the thickness of the barrier film of532.0 nm on the bottom surface facing away from the plasma. The ratio ofthe thicknesses of the film on the top and bottom surfaces isapproximately 4.25.

The thickness of the barrier film on the top surface of the wafer loadedat an acute angle is 2.266 μm which is greater than the thickness of thebarrier film on the top surface of the wafer loaded perpendicular whichis 1.503 μm. Additionally, the thickness of the barrier film on thebottom surface of the wafer loaded at an acute angle is 532.0 nm whichis greater than the thickness of the barrier film on the bottom surfaceof the wafer loaded perpendicular which is 148.8 nm. This demonstratesthat the film thicknesses on the top and bottom surfaces are greaterwhen the wafer is mounted at an angle relative to the electric fielddirection.

In the experiment described above, the orientation of the substrate waschanged to achieve better coverage of the wafer. Additionally, and asdiscussed above regarding FIGS. 3( a) and 3(b), the direction ofincoming reactants can be changed to achieve the same purpose. FIGS. 8(a), (b), and (c) show a schematic depiction of a substrate having aparticle and incoming ions from varying directions. As shown in FIG. 8,incoming ions from a source of barrier film material may be directedtowards a substrate surface at varying angles such as perpendicular tothe substrate surface as shown in FIG. 8( a) or at an angle to thesurface of the substrate as shown in FIGS. 8( b) and (c). Directing asource of barrier film material at an angle such as those shown in FIGS.8( b) and (c) will coat the shadow regions of the substrate with aparticle. This is described in more detail above with regard to FIGS. 3(a) and 3(b). Furthermore, FIGS. 3( a) and 3(b) show a substrate inrelative motion with respect to two angular sources. As shown, the firstsource 320 coats one side of the particle 310 and substrate 300 whilethe second source 330 coats the other side of the particle 310 andsubstrate 300. Such sequential deposition leads to uniform coverage ofthe particle, as further demonstrated by the results of the experimentsdiscussed above. This sequential deposition technique may be part of aroll-to-roll process or other type of fabrication technique.

It is understood that the various embodiments described herein are byway of example only, and are not intended to limit the scope of theinvention. For example, many of the materials and structures describedherein may be substituted with other materials and structures withoutdeviating from the spirit of the invention. The present invention asclaimed may therefore include variations from the particular examplesand preferred embodiments described herein, as will be apparent to oneof skill in the art. It is understood that various theories as to whythe invention works are not intended to be limiting.

1. A method of depositing a barrier film over a substrate, the methodcomprising: directing a first source of barrier film material toward asubstrate in a first direction at an angle θ relative to the substrate,wherein 0°<θ<85°.
 2. The method of claim 1, wherein directing the firstsource is performed using a plasma deposition process.
 3. The method ofclaim 1, wherein directing the first source is performed using an atomiclayer deposition process.
 4. The method of claim 1, wherein the barrierfilm material comprises a material type selected from the groupconsisting of: an oxide, a nitride, a ceramic, and an organic-inorganichybrid.
 5. The method of claim 1, wherein the barrier film material hasa water vapor transmission rate of not more than 10⁻² g/day/m².
 6. Themethod of claim 1, wherein the first source is a linear source.
 7. Themethod of claim 1, wherein 30°<θ<60°.
 8. The method of claim 1, furthercomprising: directing a second source of barrier film material toward asubstrate in a second direction at an angle φ relative to the substrate,wherein 95°<φ<180°.
 9. The method of claim 8, wherein 120°<φ<150°. 10.The method of claim 8, wherein the second source of barrier filmmaterial is the same as the first source of barrier film material. 11.The method of claim 1, further comprising: directing a second source ofbarrier film material toward a substrate in a second direction at anangle φ relative to the substrate, wherein 85°<φ<95°.
 12. The method ofclaim 10, further comprising: subsequent to directing the first sourceof barrier film material toward the substrate, rotating the substratethrough an angle equal to φ−θ.
 13. The method of claim 10, furthercomprising: subsequent to directing the first source of barrier filmmaterial toward the substrate, rotating the first source of barrier filmmaterial through an angle equal to φ−θ.
 14. The method of claim 10,further comprising: subsequent to directing the first source of barrierfilm material toward the substrate, rotating the substrate in the planeof the substrate.
 15. The method of claim 1, further comprising:providing an electric field having a field direction; and providing thesubstrate at the angle 0 relative to the field direction.
 16. The methodof claim 1, wherein the substrate comprises a substantially planar firstportion and a substantially non-planar second portion.
 17. The method ofclaim 16, wherein the substantially non-planar second portion comprisesa particle disposed over the first portion.
 18. The method of claim 1,wherein the substrate comprises an OLED.
 19. The method of claim 18,wherein the OLED is flexible.
 20. The method of claim 1, wherein thesubstrate is flexible.
 21. The method of claim 1, further comprising astep of depositing an OLED over the substrate.
 22. A method ofdepositing a barrier film over a substrate, the method comprising:directing a plurality of N sources of barrier film material toward asubstrate, each source being directed at an angle θ_(n) specific to thesource, relative to the substrate, wherein for each angles,0°<θ_(n)<180°, and for at least a first of the angles θ₁, 0°<θ₁<85°. 23.The method of claim 22, wherein, for at least a second of the angles θ₂,95°<θ₂<180°.
 24. A deposition system comprising: a first source ofbarrier film material configured to direct a barrier film material in afirst direction; and a substrate support; wherein the first source ofbarrier film material and the substrate support are positionable to forma relative angle θ between the first direction and a substrate supportedby the substrate support, and wherein 0°<θ<85°.
 25. The system of claim24, wherein the first source comprises an electric field generatorconfigured to generate an electric field having a field direction in thefirst direction.
 26. The system of claim 24, wherein the first source isfixed, and the substrate support is positionable relative to the firstsource.
 27. The system of claim 24, wherein the first source of barrierfilm material is configured to direct a barrier film material in thefirst direction using a plasma deposition process.
 28. The system ofclaim 24, wherein the first source of barrier film material isconfigured to direct a barrier film material in the first directionusing an atomic layer deposition process.
 29. The system of claim 24,wherein the barrier film material comprises a material type selectedfrom the group consisting of: an oxide, a nitride, a ceramic, and anorganic-inorganic hybrid.
 30. The system of claim 24, wherein thebarrier film material has a water vapor transmission rate of not morethan 10⁻² g/day/m².
 31. The system of claim 24, wherein the first sourceis a linear source.
 32. The system of claim 24, wherein 30°<θ<60°. 33.The system of claim 24, further comprising: a second source of barrierfilm material configured to direct a barrier film material in a seconddirection, wherein the second source of barrier film material and thesubstrate support are positionable to form a relative angle φ betweenthe second direction and the substrate supported by the substratesupport, and wherein 95°<φ<180°.
 34. The system of claim 33, wherein120°<φ<150°.
 35. The system of claim 33, wherein the second source ofbarrier film material is the same as the first source of barrier filmmaterial.
 36. The system of claim 24, further comprising: a secondsource of barrier film material configured to direct a barrier filmmaterial in a second direction, wherein the second source of barrierfilm material and the substrate support are positionable to form arelative angle φ between the second direction and the substratesupported by the substrate support, and, wherein 85°<φ<95°.
 37. Thesystem of claim 35, further comprising: subsequent to directing thefirst source of barrier film material toward the substrate, rotating thesubstrate through an angle equal to φ−θ.
 38. The system of claim 35,further comprising: subsequent to directing the first source of barrierfilm material toward the substrate, rotating the first source of barrierfilm material through an angle equal to φ−θ.
 39. The system of claim 35,further comprising: subsequent to directing the first source of barrierfilm material toward the substrate, rotating the substrate in the planeof the substrate.
 40. The system of claim 24, wherein the substratecomprises a substantially planar first portion and a substantiallynon-planar second portion.
 41. The system of claim 40, wherein thesubstantially non-planar second portion comprises a particle disposedover the first portion.
 42. The system of claim 24, wherein thesubstrate comprises an OLED.
 43. The system of claim 42, wherein theOLED is flexible.
 44. The system of claim 24, wherein the substrate isflexible.
 45. The system of claim 24, further comprising a step ofdepositing an OLED over the substrate.
 46. A system for depositing abarrier film over a substrate, the system comprising: a plurality of Nsources of barrier film material, each source configured to direct abarrier film material in a direction; and a substrate support; whereineach source of barrier film material is positionable to form a relativeangle θ_(n), specific to the source, between the direction and asubstrate supported by the substrate support, and wherein for each ofthe angles, 0°<θ_(n)<180°, and for at least a first of the angles θ₁,0°<θ₁<85°.
 47. The system of claim 46, wherein, for at least a second ofthe angles θ₂, 95°<θ₂<180°.
 48. The system of claim 46, wherein at leastone of the N sources is a linear source.